Summary A rock physics model is presented to calculate the effective resistivity of a rock with partially interconnected fluid inclusions or cracks. The model uses the differential effective medium models and the probability of interconnection between inclusions. The level interconnection between the fluid inclusion is controlled by the volume fraction of the fluid and the aspect ratio of the inclusions. The model is independent of inclusion size and assumes a statistically random distribution of inclusions. Introduction Electrical resistivity is an important physical property measurement for reservoir characterization.